W. T. Schaller — Crystallized Turquoise from Virginia. 35 



Art. V. — Crystallized Turquoise from Virginia; by 

 Waldemar T. Schaller. 



Introduction. 



A sample of a bright blue mineral, from near Lynch Sta- 

 tion, Campbell County, Virginia, was brought to the Geolog- 

 ical Survey for identification by Mr. J. H. Watkins. As a 

 few preliminary tests failed to identify the mineral with any 

 known species, a complete study of it was undertaken. The 

 results obtained show that the supposed new mineral is identi- 

 cal with turquoise. The chief interest, however, lies in the 

 fact that this turquoise is well crystallized and it was possible 

 to measure several of the minute crystals and determine thereby 

 the crystallography of the mineral. I am deeply indebted to 

 Mr. Watkins for his kindness in furnishing the material (now 

 deposited in the United States National Museum) and in allow- 

 ing this description to be published. 



The matrix of the specimen consists of irregular fragments 

 of glassy quartz of various sizes, cemented together by thin 

 layers of turquoise crystals. On one side of the specimen the 

 turquoise forms a drusy, botryoidal layer, cavernous in texture 

 and including many small irregular fragments of the glassy 

 quartz. The turquoise, with its many included quartz frag- 

 ments, polishes well and makes a very handsome ornamental 

 stone. 



The spheres, bristling with minute crystals, which form 

 the botryoidal surface, average about two or three millimeters 

 in diameter. The individual crystals rarely are as much as a 

 third of a millimeter long, being usually smaller and much 

 thinner. 



General description of mineral. 



The turquoise is bright blue in color and vitreous in luster. 

 Cleavage is present, possibly in two directions. The mineral 

 is brittle and has a hardness of about 5, though the minute 

 size and brittleness of the crystals make it difficult to deter- 

 mine the hardness closely. The density of the sample ana- 

 lyzed, determined with a pycnometer, is 2*816, which, when 

 corrected for the 12*57 per cent insoluble material (mostly 

 quartz) present (see analysis beyond), gives for the pure tur- 

 quoise the value 2*84. 



Examined under the microscope, the crystals are clear and 

 transparent and the material is very pure. Pleochroism is dis- 

 tinct, from colorless to pale bluish. Extinction is inclined on 

 all sections and, as verified by the measurements, the crystals 



